Add/replace subtitle to an already authored DVD

[ernstblaauw]

I've made a movie for a youth organization as a volunteer. The DVD has some subtitles, because the youth-organization uses the movie for fundraising and for their contacts in other languages.
I discovered some mistakes in the subtitles I made. Is it possible to add or replace a subtitle stream on the DVD, without having to reencode the MPEG2? Because I do not have the source anymore (uncompressed videofiles take a lot of space), it is no option to reencode from the source. Reencoding using the existing DVD will drop quality.
Has anyone ideas how to do this?

[Malcolm]

Use my guide for replacing audio.
Here it is: UPDATED: Compressing Audio before Shrinking a DVD (LPCM/ac3 5.1ch -> mp2/ac3 2ch) (http://forum.doom9.org/showthread.php?threadid=84887) Just leave the audio as it is and replace the subtitle instead. The steps are basically the same.

Greetings,
Malcolm